Method of and means for producing alternating currents



Nov. 23 1926. 1,608,316 r A. w HULL METHOD OF AND MEANS FOR PRODUCINGALTERNATING CURRENTS Filed Jan. 29. 1920 Fig, 2

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Albert W Hull,

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' UNETED STATES PATENT @FFICE.

ALBERT W. HULL, OF SCEENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRICCOMPANY, A CQBEQRA'EION OF NEVJ YGRK.

IvIETHOD OF AND IvIEANS FOR PRODUCING ALTERNATZNG CURRENTS.

Application filed January 29, 1920.

My present invention relates to the production of alternating currentsand more particularly continuous high frequency alternating currentssuch as are commonly employed for radio signaling.

The object of my invention is to provide a simple and convenientapparatus for producing high frequency currents from a direct currentsource or a pulsating current source of comparatively low frequency.

In carrying my invention into effect I employ an electron dischargedevice having an electron emitting cathode and an anode enclosed in anevacuated receptacle and preferably arranged in circular symmetry withrespect to each other about an axis. The electrodes of this device areincluded in a circuit containing a source of current. The currentflowing between the two electrodes may be controlled or varied inamplitude by means of a magnetic field in the receptacle in a directionparallel to the aXis of the electrodes, or at right angles to theelectrostatic field between the electrodes. If

this magnetic field is varied between certain limits, depending in eachcase upon the structure of the device and the voltage applied to theelectrodes, the current flowing between the electrodes may be variedbetween a maximum value which may be the value of the current whichwould flow in the absence of anymagnetic field and a minimum value whichmay be substantially zero. In practice it will probably be founddesirable in most cases to provide a constant magnetic field of such avalue that the current flowing between the electrodes will be somewhatreduced from the amount which would flow in the absence of a magneticfield. The current flowing in the device may then be varied betweenmaximum and minimum values by means of a supplementary variable magneticfield which is produced by means of the current flowing between theelectrodes and which alternately assists and opposes the constantmagnetic field.

The novel features which I believe to be characteristic of my inventionare set forth with. particularity the appended claims Serial No.354,913.

The invention itself, however, both as to its organization and method ofoperation will best be understood by reference to the followingdescription taken in connection with the accompanying drawing in whichFig. 1

illustrates diagrammatically one way in which my invention may becarried into effect, and Fig. 2 is a characteristic curve showing therelation between the current flowing between the electrodes at constantof tubular form and which contains a filamentary cathode 2 and an anode3 of cylindrical form, the two electrodes being arranged in circularsymmetry with respect to each other; that is, the active surfaces of thetwo electrodes are substantially surfaces of revolution about a commonaxis which is preferably the major axis of the receptacle 1. V'Vhilethis arrangement of electrodes is desirable for securing the bestresults it is not essential as satisfactory results may be obtained witharrangements of the electrodes which do not involve circular sym metry.A source of current 4 is connected to the two terminals of the cathode 2for heating it to incandesceuce to .cause it to emit electrons forcarrying current across the evacuated space between the two elec trodes.trodes 2 and 3 includes a source of current 5 an impedance device 6, aninductance rep An external circuit between elecresented conventionallyat 7 but which actually is wound around the receptacle 1, and a variablecapacity 8 in shunt to the inductance. A constant magnetic field isprovided by means of a coil 9 likewise surrounding the receptacle 1, andsupplied with current from a direct current source 10, the strength ofthe magnetic field thus furnished being adjustable to a desired value bymeans of a variable resistance 11. It may also be desirable to include achoke coil 12 in the circuit which supplies current to the coil 9 inorder to prevent alternating current from circulati'rg in that circuitby reason of the ind a relation between coils 7 and 95 109 substantiallyradial paths.

The circuit between electrodes 2 and 3 may also include a coil 13 whichis coupled to a. coil 14, which is included in circuit with the antenna15, thereby supplying the high frequency current which is generated tothe antenna circuit.

When the cathode is maintained at a suitable temperature by the heatingcurrent and asuitable voltage is impressed upon the electrodes, currentwill flow in the plate or output circuit, 5, 7, l3, 6. ll ith nomodifying magnetic field the value of this current is determined byvarious factors, among which are the impressed voltage, cathode temperature, size and geometric relation of the electrodes and the resistanceof the output circuit. The electrons which carry or con stitute thiscurrent travel outwardly from the cathode to the surrounding anode inVlhen the magnetic field is generated in a direction substantiallyparallel'to the axis of the electrodes and substantially at a rightangle to the paths of the electrons, the electrons are deflected andcaused to travel in spiral paths about the cathode on their way to theanode. As the field strength is increased the spiral paths of theelectrons become longer until finally at a critical magneticfieldstrength, characteristic of any particular device, som-eot-theelectrons tail to reach theanode by reason of this deflection, therebycausing a decrease in the current. When the field strength is stillfurther increased above this-criticalvalue the electron current fallsand is substantially reduced to zero.

The relation between the magnetic field and current flowing in the plateor output circuit is indicated by the diagram of Fig. 2, the values ofthe magnetic field being plotted as abscissae and the correspondingcurrent values-as ordinates, the impressed voltage being constant. Itwill be observed that as the strength of the magnetic field is increasedifrom zero','the"current remains substantially constant until themagnetic field has reached a value represented by ac. Further increaseof field strength produces a rapid reduction of current until at a fieldstrength 0.7), the current has fallen to substantially zero.

The apparatus which I have described may be employed in various ways toproduce oscillations and various explanations may be advanced as to themanner in which the apparatus-operates to produce oscillations. l l hileI do not wish to limit myself to any particular method of operation, thefollowing description is given "to indicate one manner in which theapparatus may be c erated.

Tie constant magnetic field may be adjusted to a value substantiallyequal to or somewhat greater than that represented by 0a in Fig. 2. Themagnetizing coil 7 may be so arranged and connected to the source 5 thatthe current flowing therethrough from this source will produce amagnetic field which adds to the constant magnetic field. Under theseconditions when the circuits are completed current will start to flow inthe plate circuit but this current instead ot coming up to the maximumvalue will only rise to a value intermediate the maximum and minimumvalues. In building up to this value at which the combined magneticfields produced by coils and 9 will prevent further increase of current,the condenser 8 will be charged. When the current in the plate circuitreaches the maxi- 9 mum value to which it can build up under theseconditions the condenser 8 discharges through coil 7 producing a currentin the opposite direction to that produced by the source 5. The magneticfield produced by this current will oppose the constant mag netic fieldand allow the building up again of current through the coil 7 from thesource b. The building up of this current will.

again pro-duce a magnetic field which adds to that of the coil 9 andcauses the current to decrease. The. frequency of these changes incurrent will depend upon the natural period of the oscillating circuitwhich comprises the condenser 8 and coils 7 and 13. Current flowing inthe plate circuit may be considered as a direct current having analternating component superimposed thereon, this alternating componentbeing the component which is effective in varying the magnetic fieldinthe device, and hence varying the current in the plate circuit. Thisaction is assisted by the impedance 6.

The alternatingcurrent produced in this way, it of radio frequency, maybe modu lated or interrupted in any desired way for radio signalingpurposes either telephonic or telegraphic. It is also apparent that thealternating current produced may be employed torwire signaling or forany other purpose for which it is desired to employ alternatingcurrents.

Vi hile I have shown and described on y one form of my invention, I donot wish to be limited to this particular form as it is apparent thatmany variations in the structure of the devices employed, as well as inthe circuit connections used, may be made without departing from thescope of my invention as set forth in the appended claims.

Va hat I claim as new and desire to secure by Letters Patent of theUnited States. is

1. The combination in a system for producing alternat ng currents of anelectron dischuge device comprising an evacuated receptacle containingcathode adapted to emit electrons independently oi? gas ionization andan anode arranged in substantially circuliar symmetry and unobstructedspacial Ill) Ill)

relation with respect to said cathode, means for producing a constantmagnetic field In said receptacle in the space between said electrodes,an external circuit between said cathode and anode containing a sourceof.

current, and means for producing by current flowing in said circuit amagnetic field which is superimposed upon the constant magnetic field.

The method of producing alternating currents which consists in producinga stream of electrons in substantially radial paths between an electronemitting cathode and a cooperating electrode, producing a constantmagnetic field in a direction substantially at a right angle to thepaths of the electrons and periodically substantially interrupting theelectron stream between cathode and cooperating electrode by means ofmagnetic field produced by current carried by said electron stream andsuperimposed upon said constant magnetic field.

The method of producing alternating currents which consists in producinga stream of electrons in substantially radial paths between an electronemitting cathode and a cooperating electrode, and periodicallysubstantially interrupting the electron stream bet-ween cathode andanode by means of a magnetic field which is in a direction substantiallyat a right angle to the paths of the electrons and which is produced bycurrent carried by said. electron stream.

4-. The combination in a system for producing alternating currents of anelectron discharge device comprising an evacuated receptacle containinga cathode adapted to emit electrons independently of gas ionization andan anode arranged in substantially circular symmetry and unobstructedspacial relation with respect to said cathode, means for producing aconstant magnetic field in said receptacle, an external circuit betweensaid cathode and anode containing a source of current and an inductivewinding surrounding said receptacle and supplied with current from saidexternal circuit.

The combination in a system for producing alternating currents of anelectron discharge device comprising an evacuated receptacle containinga cathode adapted to cmt electrons independently of gas ionization andan anode, means for producing a constant magnetic field in saidreceptacle in the space between said electrodes in a directionsubstantially at a right angle to the path of the electrons, an externalcircuit between said cathode. and anode containing a source of current,an oscillatory circuit which is resonant to the frequency of thecurrents to be produced, and an inductive Winding surrounding Saidreceptacle, included in said oscillatory circuit and supplied withcurrent trom said external circuit.

6. The combination in a system for producing alternating currents of anelectron discharge device comprising an evacuated receptacle containinga cathode adapted to emit electrons independently of gas ionizationarranged in substantially circular symmetry and unobstructed spacialrelation with respect to said cathode, means for producing a constantmagnetic field in said receptacle in the space between said electrodes,an external circuit between said cathode and anode conta ning a sourceof current, and an inductive winding surrounding said receptacle andconnected in series relation in said external circuit.

7. The combination in a system for producing alternating currents of anelectron discharge device comprising an evacuated receptacle conta ninga cathode adapted to emit electrons independently of gas ionization andan anode arranged in unobstructed spacial relation with respect to saidcathode, means for producing a constant magnetic field in saidreceptacle, an external circuitbe'twcen said cathode and anodecontaining a source of current, an inductive winding surrounding saidreceptacle and connected in series relation in said external circuit,and a capacity in mg.

8. The combination in a system for pro-' duc ng alternating currents ofan electron discharge device comprising an evacuated receptaclecontaining a cathode adapted to emit electrons independently of gasioniza t-ion and an anode, means for producing a constant magnetic fieldin said receptacle in the space between said electrodes, an externalcircuit between said cathode and anode containing a source of current,an oscillatory circuit which is resonant to the frequency of thecurrents to be produced, and an inductive winding surrounding saidreceptacle, included in said oscillatory circuit, and connected inseriesrelation in said external circuit.

9. The combination in a system for producing alternating currents of anelectron discharge device comprising an evacuated receptacle containinga cathode adapted to emit electrons independently of gas ionization andan anode arranged in substantially circular symmetry and unobstructedspacial relation with respect to said cathode, an external circuitbetween said cathode and anode containing a source of current, and aninductive winding surrounding said receptacle and supplied with currentfrom said external circuit so as to produce a magnetic field in thespace between said electrodes.

10. Means for producing alternating currents comprising an electrondischarge device having a cathode adapted to emit electronsindependently of gas ionization and an anode arranged in substantiallycircular symmetry and unobstructed spacial relation shunt to saidinductive windill) with respect to said cathode enclosed in an evacuatedreceptacle, an external circuit between said electrodes containing asource of current, an impedance in said circuit, means for producing aconstant magnetic field in said" receptacle in the space between I saidelectrodes, and means for producing by energy supplied from said sourceof current a variable magnetic field which is superimposed upon theconstant magnetic field.

11. The combination in a system for pro ducing alternating currents ofan electron discharge device comprising an evacuated receptaclecontaining a cathode adapted to emit electrons independently of gasionization and ananode arranged in substantially circular symmetry andunobstructed spacial relation with respect to said cathode, an ex ternalcircuit between said cathode and anode containing a source of current,means for producing a constant magnetic field in said receptacle andmeans for producing by energy supplied from said source of current, avariable magnetic field which is superimposed upon the constant magneticfield.

12. Thecombination in a system for producing alternating currents of anelectron discharge device comprising an evacuated receptacle containinga cathode adapted to emit electrons independently of gas ionization andan anode arranged in substantially circular symmetry and unobstructedspacial relation with respect to said cathode, an e2:- ternal circuitbetween said cathode and anode containing a source oi. current, andmeans for producing by current flowing in said current a magnetic fieldin the space between said electrodes.

13. The combination in a system for producing alternating currents of anelectron discharge device comprising an evacuated receptacle containinga cathode adapted to emit electrons independently of gas ionization andan anode arranged in substantially circular symmetry with respect tosaid cathode, an external circuit between said cathode and anodecontaining a source of current, an oscillatory circuit and an inductivewinding surrounding said receptacle and included in said oscillatorycircuit and connected in series relation in said external circuit.

14. The combination in a system for producing alternating currents of anelectron discharge devlce comprising an. evacuated receptacle containinga cathode adapted to emit electrons independently of gas ionization andan anode arranged in substantially circular symmetry and unobstructedspacial relation with respect to said cathode, means for producing aconstant magnetic field in said receptacle in the space between saidelectrodes, an external circuit between said cathode and said anodecontaining a source of current, an oscillatory circuit supplied withcurrent from said external circuit, and means for producing a magneticfield by current in said oscillatory circuit which will be superimposedupon said constant magnetic field. V

15. The method of operating an electron discharge device, having anelectron emitting cathode and an anode enclosed in an evacuatedreceptacle, to produce oscillations which consists in producing aconstant magnetic field in the space between the electrodes, producingbetween the electrodes a flow or current which is carried by negativeelectrons moving in substantially radial paths substantially independentof gas ionization and producing by means of current flowing between saidelectrodes a variable magnetic field which is superimposed upon theconstant magnetic field in the space between the electrodes and which isof sulficient value to periodically substantially interrupt the flow ofelectrons.

16. The method of operating an electron discharge device, having anelectron emitting cathode and an anode enclosed in an evacuatedreceptacle, to produce oscillations which consists in applying apotential to said electrodes to produce a fiow of current between saidelectrodes which is carried by negative electrons substantiallyindependent of gas ionization, and producing by means or current flowingbetween said electrodes a variable magnetic field in the space betweensaid electrodes in a direction substantially at right angles to theelectrostatic field between said electrodes and which is of suflicientvalue to periodically substantially interrupt the flow of electrons.

17-. The method or operating an electron discharge device, havinganelectron emit ting cathode and an anode enclosed in an evacuatedreceptacle, to produce oscillations which consists in applying apotential to said elecrocles to produce a flow of current between saidelectrodes which is carried by negative electrons substantiallyindependent of gas ionization, producing a constant magnetic fieldbetween said electrodes in a direction substantially at right angles tothe electrostatic field between said elec trodes and producing by meansof current flowing between said electrodes a variable magnetic fieldwhich is superimposed upon said constant magnetic field and which is ofsnificient value to periodically substantially interrupt the flow ofelectrons.

18. The method of operating an electron discharge device, having anelectron emitting cathode and an anode enclosed in an evacuatedreceptacle, to produce oscillations which consists in applying apotential to said electrodes to produce a flow of current between saidelectrodes which is carried by negative electrons substantiallyindependent of gas ionization, producing a constant between saidelectrodes, a variable magnetic In witness whereof, I have hereunto setmagnetic field between said electrodes in a assists and opposes saidconstant magnetic direction substantially at right angles to field andwhich is ofsufficient Value when the electrostatic field between saidelectrodes it assist-s said constant magnetic field to 10 and producingby means of current flowing substantially interrupt the flow ofelectrons.

field which is superimposed upon said conmy hand this 27th day ofJanuary 1920. stant magnetic field and which alternately ALBERT W. HULL.

